Many popular types of rifles such as lever action rifles employ tubular magazines, in which a single line of cartridges is stored in a cylindrical tube parallel to and just below the rifle barrel. The cartridges are arranged nose first, with a compressed spring and piston forward of the nose of the forward most cartridge. The spring pressure transmits through the row of cartridges, and forces the rear most cartridge into the action when the action is cycled.
Because the nose of each cartridge in the tube presses against the rear of the next cartridge, this raises a critical safety concern. Centerfire cartridges have primers centered on the base of the cartridge, and it is essential to ensure that the nose of one bullet does not act like a firing pin that strikes the primer of the next bullet. Such forces can occur if a rifle is dropped, such as from an elevated tree stand, or from recoil upon discharge. Thus, sharply pointed bullets common to other types of rifles employing box magazines (in which the cartridges are positioned side-by-side) are not suitable for tube-magazine rifles.
Rifles with tubular magazines are limited to rimfire cartridges (which do not have a central primer and require a sharp pinching of the rim to discharge) and to centerfire cartridges having broad flat noses. Blunt, rounded nose bullets have been employed, but these are regarded as more risky than flat nosed bullets. Typically, the flat nose of a suitable bullet has a diameter of approximately 60% or greater than that of the primer. This ensures any force transmitted to the primer is distributed over a large enough area to ensure that primer discharge will not occur. Cartridges with heavier bullets generally have larger diameter flat noses, to account for the increased force that the added mass of a stack of cartridges can generate upon dropping a loaded rifle, and the increased recoil associated with such cartridges. The noses of such bullets are generally formed of exposed lead and are not fully jacketed to provide further safety.
While effective to ensure safety, flat nosed or other blunt bullets are aerodynamically inefficient compared to the sharply pointed bullets used in other rifles. This means that they lose more velocity as a function of distance traveled than a sharp pointed bullet, due to increased air resistance. This effect is greatest over longer distances. Because of this higher rate of velocity loss blunt bullets carry less energy downrange than do pointed bullets. In addition, the reduced velocity at distance leads to greater bullet drop and crosswind drift, requiring more compensation by and opportunity for error from the shooter.
A suitable safe, blunt bullet for a tubular rifle magazine will generally have a ballistic coefficient (BC) of approximately 0.200 depending on the caliber and weight of the bullet. Sharply pointed bullets, of comparable caliber and weight, have BC values typically of 0.250 to 0.350. Thus, a lever action rifle chambered in 30-30 Winchester is considered effective for deer hunting only out to about 100-150 yards, while cartridges with spire-point bullets of comparable weight and muzzle velocities are effective for deer beyond 250 yards.
For applications other than tube-feed rifles, it is often important that bullets have an expansion capability. An expanding bullet is often more effective to disable or stop the intended target. For hunting, this means a more lethal and humane effect on game. For self defense, police, and military applications, it means that an attacker is more readily incapacitated, ending the attack.
One common type of expanding bullet is a hollow point bullet. This has a central cavity or opening at the nose of the bullet, which facilitates the hollow forward end flaring outward upon impact to create a broader profile. This is more disruptive of tissue, providing the increased effectiveness. However, hollow-point bullets have certain disadvantages. The amount by which the bullet expands is critical, with under- and over-expansion limiting effectiveness. If the bullet does not adequately expand, then it has less disruptive effect leading to reduced stopping power, and may over penetrate the target, endangering bystanders or at least limiting effectiveness by failing to deliver some of the bullet's energy to the target. An over-expanded round delivers all its energy to the target, but has limited penetration. This also diminishes the intended effectiveness against targets.
Moreover, if a criminal attacker is wearing heavy clothing such as denim or leather, the material may clog up the hollow point, preventing or substantially reducing expansion. Other problems with conventional hollow point bullets is that an off-axis impact on hard material such as sheet metal or glass can tend to cause the hollow point leading edge to bend, closing it up and preventing expansion upon eventual impact with the target.
Some bullets have hollow points formed in the bullet body (typically formed of a lead alloy with a copper alloy jacket) and with the hollow cavity filled with an element of a different material. Rifle bullets may have a hollow cavity filled with a pointed tip element to provide an aerodynamic profile, and which facilitates expansion upon impact at high velocities. Certain pistol bullets employ a round plastic ball that partially fills a bullet's cavity, preventing clogging with clothing material, and facilitating expansion. While providing some benefits, there remains a need to generate more effective and controlled expansion of bullets.
A particular concern is that while high-velocity rifle bullets readily expand upon impact, lower velocity rounds expand less reliably. This is a particular concern for compact pistols with short barrels in smaller calibers often carried for self defense. In certain calibers, even a hollow-point round not suffering from clogging with clothing material may not expand sufficiently. Moreover, a bullet designed for expansion at lower velocities may excessively expand when fired from a gun with a longer barrel generating higher muzzle velocity.
The present invention overcomes the limitations of the prior art by providing a bullet or a cartridge containing a bullet having an elongated body with a forward end and an opposed rear end. The body has an intermediate cylindrical portion between the rear and forward ends, and the front end of the body defines a cavity. A resilient nose element is received in the cavity. The nose element may be an elastomer, and may be a cylindrical body. The cavity may be a cylindrical bore, and the nose element may be closely encompassed within the bore. The forward end of the nose element may be flat, and may be flush with the forward end of the body.